Metabolic biomarkers improved with short walks after periods of sitting

Action Points

Even a little bit of exercise during long spells of sitting had positive short-term biomarker effects for kids in a small study.

Note that the study findings suggest that interrupting sedentary behavior may be a promising prevention strategy for reducing cardiometabolic risk in children.

Even a little bit of exercise during long spells of sitting had positive short-term biomarker effects for kids in a small study.

Twenty-eight healthy children age 7-11 were required to either sit for 3 hours, or were interrupted every 30 minutes for a short walk over two sessions of the study, each lasting 3 hours. Researchers led by Britni Belcher, PhD, MPH, at the National Cancer Institute in Bethesda, Md., found that those who got up to walk had a 32% lower insulin area under the curve (P<0.001), 17% lower C-peptide area under the curve (P<0.001), and 7% lower glucose area under the curve (P=0.018) compared with kids who sat for the entire 3 hours.

In addition, mixed model results suggested that insulin and free fatty acid concentrations were lower in the walking group (P=0.036 and P=0.009, respectively).

"These findings suggest that interrupting sedentary behavior may be a promising prevention strategy for reducing cardiometabolic risk in children," wrote the authors.

In the study, there were no significant differences between the groups in terms of free fatty acid, triglycerides, and cortisol area under the curve (AUC). There was also no difference between the groups in terms of lunchtime meal energy intake after the sitting periods (P=0.85).

Children spend about 6 hours a day sitting on average, according to the authors, and other studies have linked sitting to a heightened risk of obesity and insulin resistance. And another study found that regardless of the amount of time children spent sitting around, exercise improved their cardiometabolic risk factor.

None of the children were overweight in the study. Participants were recruited by flyers, listservs, word of mouth, and social media; children with impaired glucose tolerance or type 2 diabetes were excluded. During the sessions, children watched movies, read, colored, or did homework, and afterwards they were given a buffet.

The participants wore a device that monitored sleeping and activity the week before the evaluations. There were no significant differences between the two groups during that week.

Children in the sitting group were required to remain seated for 3 hours, with limited movement, and weren't allowed to get up and move around except to go to the restroom. Those in the intervention group walked on a treadmill, at 80% of the ventilatory threshold, for 3 minutes every 30 minutes. Their heart rate was monitored to keep them near the target, and they walked six times during the test, for a total of 18 minutes.

An average interval of 20 days separated the two experimental visits. Biomarker sampling was performed 10 minutes before the study and at 0, 30, 60, 90, 120, 150, and 180 minutes. Baseline levels were calculated by averaging the first and second measurements.

The authors noted that a previous study found that among adults, interrupted sitting led to reduced insulin AUC. "Taken together, these findings suggest that interrupting sitting with short bouts of activity has an effect on acute glucose homeostasis," they wrote.

Limitations of the study included its small sample size. "Indeed, the observed effect sizes for glucose and C-peptide AUC were small, indicating that a larger sample may be needed to determine whether post-drink patterns differ," wrote the authors, adding that they did, however, have enough power to detect differences in insulin AUC.

The researchers didn't limit the participants activity before the study, but they noted that the accelerometer-measured activity in the study sample was not significantly different before each experiment. In addition, the results may not generalize to children who are overweight or obese.

"Additional research should explore how the duration and patterns of sedentary behaviors may produce negative health effects in children and whether these effects can be overcome by interruption with short periods of moderate-intensity walking," the authors concluded.

The authors of the study disclosed no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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